Single-motor bots crawl, swim and climb with a wiggle and a wave

Over the years, we've seen a number of robots inspired by the animals kingdom – from jumpers and crawlers to swimmers and fliers. Inspired by the movement of snakes, an Israeli research team has now developed a bot that's said to be the first in the world to produce pure wave motion using a single motor.

The Single Actuator Wave-like Robot (SAW) has been created by Dr. David Zarrouk, of the university's Mechanical Engineering Department, and a team of students at the Bioinspired and Medical Robotics lab. "The design was originally intended to be used for crawling inside the
intestines as a self-propelled endoscope (for filming the intestines and
biopsies)," Zarrouk told us. "I had been working on this subject for many years and a
couple of years ago I came up with this design which produces
continuously advancing wave."

Central to its novel movement is a spiral-shaped rod that's fed though linked 3D-printed slats running down the body. As the single motor rotates the helix spine, continuous wave motion of the body results and the links push forward or backward when they come into contact with the ground.

This dynamic motion is reported to allow the SAW to move over different surfaces (such as sand, grass or gravel) and climb over obstacles or through tunnels. The continuous wave motion body is attached to a wheeled head, which is used for steering, not to aid locomotion. There's even a waterproof version that can swim at 6 cm per second.

It's a quick mover, too, with a top speed of 57 cm per second. "We formulated the speed as a function of the speed wave, wave length,
thickness of the wave and its amplitude, revealed Zarrouk. "We realized from our model that
it possible for the robot to crawl even faster than its own wave speed
and we managed to prove this experimentally (our robot with the
"dentals" moved 13 percent faster than the speed of the advancing wave).

The wave motion mechanism can be produced in different sizes, scaling it up for search and rescue missions or shrinking down for medical applications.

"In the future, we intend to shrink it further to less than 1 cm in
diameter (which is possible thanks to the simple design and single
motor)," Zarrouk said. "We also intend to make possible larger version in which we
attach two robots through an actuated U joint in order to replace the
wheels. "

He also points to the wave bot being something of a tough cookie, easy to manufacture and reliable. "It is easy to manufacture because it has an extremely simple design," he explained. "It
has a light weight and no need for complex controllers to make the wave
motion. The power density is very high as all the work is being [undertaken] by a
single motor with no "sleeping" motors. It almost doesn't break even
though it is made of 3D-printed plastic. We made lots of runs on rough
surfaces and the robot always succeeded in crawling over them in a
single shot and no maintenance in between."

A paper on the SAW project has been published in the journal Bioinspiration & Biomimetics. You can see various SAW flavors in action in the video below.